DNA damage due to phototherapy: Single or double lights?

Abstract

On ward rounds I have sometimes been asked by medical students and residents whether it really matters if we put an infant on single, double or triple phototherapy lights. Can using ‘too much’ phototherapy cause damage to body cells? Phototherapy is not associated with serious side effects, and certainly over the past few decades has become much safer. In the presence of risk factors for severe jaundice e.g. ABO/rhesus incompatibility, using intensive phototherapy has been an easy answer. The benefits likely outweigh the risks anyway. However, it is not such an easy question when it comes to using single or more intensive phototherapy in the first instance in the absence of risk factors with borderline or moderately high serum bilirubin (SBR). A recent case-control study of 36 newborns showed that both conventional and intensive phototherapy increase DNA damage in cells.1 DNA damage was measured using single-cell gel electrophoresis in peripheral mononuclear cells. Interestingly the duration, but not the intensity of phototherapy correlated with the degree of DNA damage (r = 0.86, P < 0.001). The authors argued therefore that it might be more efficacious, less toxic to cell DNA and cost saving with reduced hospital stays to use intensive phototherapy for short duration than conventional phototherapy which will bring down the SBR at a slower rate. What is unclear is if this DNA damage is transient or has any long-lasting consequences.